The present invention relates to a socket wrench extension comprising a polygonal insertion member and a correspondingly designed receiving member at the other end. The insertion member comprises a locking member that partially projects from a lateral socket head surface. A pressure transmission member is axially guided in the insertion member and has a pin-shaped or key-shaped end that serves as a pressure actuation of the pressure transmission member and has another end that is a component of a mechanism for transforming an axial movement of the pressure transmission member in the direction toward the insertion member into an outward movement of the locking member.
Such locking members are provided in order to snap into position by a spring force into a matching recess of a receiving member into which the insertion member of the socket wrench extension is to be inserted. In general, this is the receiving member of a socket wrench insert. By snapping into position in the recess, the locking member prevents easy separation of the two tool parts because they are connectable and releasable only by applying a certain force. However, it often occurs that the parts become accidentally detached, for example, when the socket wrench extension with socket wrench insert connected thereto must be removed from a screw or nut when in a slightly slanted position. Between the socket wrench insert and the screw or the nut frictional forces may occur that are greater than the locking forces of the spring-loaded locking member.
A socket wrench extension of the aforementioned kind is known from U.S. Pat. No. 5,289,745. Such socket wrench extensions are embodied as a single-piece component, which, depending on its respective embodiment, has a concentrically or eccentrically arranged longitudinal bore for receiving an actuating rod. The longitudinal bore is embodied either as a throughbore or as a blind bore. While in the first case an end cap is required at the end face of the polygonally embodied insertion member, in the latter case an abutment ring, secured by a washer and a spring ring is provided in a receiving member adjacent to the bore in order to effect axial fixation of the actuation rod. A disadvantage of these known socket wrench extensions is that the axial guiding action of the guiding rod is in all cases realized by a longitudinal bore so that high standards in regard to machining tolerances for providing a precise guiding action are necessary. This makes the manufacture of such extensions very expensive. A further disadvantage of the known socket wrench extensions is that the locking member is positioned in a transverse bore within the insertion member and is secured therein by a securing screw or an end cap against falling out. This requires a great number of components, and thus results in a cost-intensive manufacture and mounting.
It is therefore an object of the invention to improve a socket wrench extension of the aforementioned kind such that with a simple assembly and reduced manufacturing costs a high functional precision is achieved.